The present invention relates, in general, to a valve system for fluid pipes and, more particularly, to an improvement in such a valve system to allow the system to be operable using pneumatic pressure or using another means in place of pneumatic pressure and to be controlled easily and precisely, and to quickly and smoothly feed fluid, thus improving operational reliability of the system.
As well known to those skilled in the art, a fluid pipe, used for feeding fluid, is provided with one or more valve systems for controlling the flow of fluid passing through the pipe.
FIGS. 1 and 2 show the construction and operation of a conventional pneumatic valve system for fluid pipes. As shown in the drawings, the conventional valve system comprises two bodies: first and second bodies 11 and 12 assembled into a single valve housing 10. An internal fluid passage 13 is longitudinally formed along the central axis of the valve housing 10 with inlet and outlet openings 13a and 13b being provided at both ends of the passage 13. In such a case, the inlet opening 13a is formed in the first body 11, while the outlet opening 13b is formed in the second body 12. An annular guide groove 13c, having a concave surface, is formed on the passage 13 at a position inside the outlet opening 13b. 
A cylindrical valve body 20, having an axial fluid passing opening 21, is axially and movably fitted in the passage 13 in a way such that the valve body 20 is reciprocable within a predetermined range in the axial direction of the valve housing 10. The above valve body 20 selectively closes the passage 13 at the first end 22 thereof when the valve body 20 is fully moved to the right in the drawings. That is, the first end 22 of the valve body 20 acts as a passage control means for opening or closing the passage 13 of the valve system. A flanged cylindrical disc 30, having two fluid passing holes 31 on its sidewall, is fixedly installed in the passage 13 at a position within the guide groove 13c. The reciprocable valve body 20 selectively comes into close contact with the flange of the disc 30 at the first end 22 when the valve body 20 is fully moved to the right in the drawings, thus closing the passage 13.
An annular pressure actuated flange 25 is exteriorly and fixedly formed on the valve body 20. The above flange 25 formes first and second air pressure chambers 15a and 15b within the valve housing 10 at opposite sides thereof while sealing the junction between the two variable chambers 15a and 15b. The first chamber 15a is provided with a first air injection port 16a, through which pneumatic pressure, or external air pressure, is injected into the chamber 15a so as to open the passage 13. The second chamber 15b is provided with a second air injection port 16b, through which external air pressure is injected into the chamber 15b so as to close the passage 13.
A fluid flow control operation of the above valve system will be described hereinbelow.
In order to open the passage 13 of the valve system, external air pressure is injected into the first chamber 15a through the port 16a, thus acting on the right-side surface of the pressure actuated flange 25. The valve body 20 is thus moved toward the fluid inlet opening 13a, and so the first end 22 of the valve body 20 is spaced apart from the disc 30. Therefore, the internal fluid passage 13 of the system is opened as shown in FIG. 1.
When the passage 13 is opened as described above, fluid, introduced into the passage 13 through the inlet opening 13a, flows into the groove 13c through the gap between the valve body 20 and the disc 30. The fluid, thereafter, passes through the fluid passing holes 31 of the disc 30 prior to being discharged from the passage 13 through the outlet opening 13b. 
When it is necessary to close the passage 13 of the valve system, external air pressure is injected into the second chamber 15b through the port 16b, thus acting on the left-side surface of the flange 25. The valve body 20 is thus moved toward the fluid outlet opening 13b, and so the first end 22 of the valve body 20 comes into close contact with the disc 30. Therefore, the internal fluid passage 13 of the system is completely closed as shown in FIG. 2.
When the passage 13 is closed as described above, fluid, introduced into the passage 13 through the inlet opening 13a, is prevented from flowing into the groove 13c. It is thus impossible for the fluid to be discharged from the passage 13 of the valve system into a pipe through the outlet opening 13b. 
However, the above valve system is problematic in that the valve body 20 is designed to be only pneumatically operated, thus failing to be precisely controlled. It is thus impossible to precisely control the opening of the valve body 20.
The above valve system is not provided with any separate means for controlling the valve body 20, the means being selectively used for actuating the valve body 20 in an emergency case wherein it is impossible to get air pressure. This reduces the operational reliability and market competitiveness of the valve system.
In addition, the valve body 20 is brought into frictional contact with the interior surface of the passage 13 during a reciprocating action thereof. Therefore, it is difficult for the valve body 20 to smoothly move within the passage 13, and so the valve body 20 may fail to accomplish a desired operation. This problem becomes worse when the air pressure, acting on the flange 25 of the valve body 20, is less than a reference level.
Another problem, experienced in the above valve system, is caused by a difference in flow rates between fluid currents within the passage 13. That is, the outside fluid current, flowing along the interior surface of the passage 13, may be easily and smoothly introduced into the guide groove 13c at a relatively high speed. However, the central fluid current, flowing along the axis of the passage 13, may be not easily or smoothly introduced into the groove 13c. This is caused by the fact that there occurs a friction between the central fluid current and the disc 30 and the central fluid current has to be moved from the central portion of the passage 13 to the guide groove 13c. Therefore, the flow rates of the fluid currents are different from each other. Due to such a flow rate difference, it is almost impossible for the fluid to quickly or smoothly flow in the passage 13.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a valve system for fluid pipes, which is designed to be operable using pneumatic pressure or using another means in place of pneumatic pressure and is designed to be controlled easily and precisely.
Another object of the present invention is to provide a valve system for fluid pipes, which effectively reduces the frictional force between relatively moved parts during an operation of the system, thus being allowed to be easily and smoothly operated.
A further object of the present invention is to provide a valve system for fluid pipes, which allows fluid to smoothly and quickly pass through the system.
In order to accomplish the above objects, the present invention provides a valve system having the following construction. Both a disc and a reciprocable valve body are provided within the internal fluid passage of a valve housing, with fluid inlet and outlet openings being formed at both ends of the passage. The valve body is designed to be normally and pneumatically operated using air pressure injected into either one of two chambers, provided at both sides of the pressure actuated flange of the valve body, through first or second injection port of the valve housing in the same manner as that of the prior art. The valve body thus comes into close contact with the disc or is moved away from the disc by air pressure so as to close or open the passage. The valve system of this invention further comprises a rotor used for centrifugally forcing the fluid as it is introduced into the passage. A fluid guide rod axially extends along the center of the passage, thus guiding the flow of fluid. The disc also has a fluid guide member, which may have a variety of fluid guide surfaces. The fluid is thus allowed to more quickly and smoothly pass through the valve system.
In addition, the valve body is movably and concentrically supported by a plurality of spring-biased valve support units. The valve body is thus movable within the passage while minimizing frictional force between the valve body and the valve housing.
The valve system of this invention also has a valve control means for selectively moving the valve body toward the fluid inlet or fluid outlet opening of the passage so as to open or close the passage, without using air pressure, when necessary.
In an embodiment, the valve control means comprises a valve control lever operated in conjunction with an annular guide groove formed on the circumferential external surface of the pressure actuated flange of the valve body. In such a case, the linear moving direction and moving distance of the valve body is determined by the rotating direction and rotating angle of the lever. In another embodiment, the valve control means is designed to operate the valve body using fluid, passing through the valve system, in place of pneumatic pressure.